7.8 Existing trees and hedgerows

Existing healthy and well-formed trees and hedgerows should be retained or moved if compromising an urban layout as specified in this guide. As well as protecting existing biodiversity and assisting with biodiversity net gain (BNG) targets, established trees provide beautiful natural features that will enhance new developments.

Through good design practices trees and hedgerows can be integrated into, and enhance, the development. To achieve this, designers should follow the guidance in British Standard 5837 – 2012 and the following additional requirements [Reference 21]:

When pavements are proposed within tree root protection zones, a non-dig, permeable paving solution will likely be required to avoid loads being transferred to the soil and roots and prevent over compaction of soils. This may result in roads and pavements being raised over existing roots.

Excavations under tree canopies, if needed, must be done by hand. No root over 25mm in diameter should be severed. Tree removal and replacement planting may be required if substantial root loss occurs.

Existing trees within proposed visibility splays must be retained. Where there is a conflict the location and design of junctions should instead be revised. Considering the location of trees early in the design process will mean that such conflicts are avoided.

Trees adopted by Surrey County Council Highways have been assigned a financial value using the Capital Asset Value for Amenity Trees (CAVAT) methodology [Reference 22]. The council will seek full compensation as per the CAVAT assessment for any removal of, or damage to existing highway trees. It should be noted that costs can be significant. An average mature oak can be valued at approximately £100,000 when using this method, and even a small ornamental tree would be valued at £3,000 [Reference 23].

References

• Reference 21: BSI (2012) BS 5837 – 2012 Trees in relation to design, demolition and construction (Return to content for reference 21).
• Reference 22: London Tree Officers Association (LTOA): https://www.ltoa.org.uk/resources/cavat (Return to content for reference 22).
• Reference 23: Surrey County Council (2016) Highways and Transport Asset Management Strategy Section 8.11 – Arboriculture (Return to content for reference 23).